In my U.S. Pat. Nos. 4,701,113; 4,690,623 and 4,799,654 I have described the coned ring elements which are able to work in the supercritical pressure range of pressures higher than 1000 atmospheres in the pumping chamber between two neighboring pumping elements. Also described in the mentioned publication are the drive means to operate the strokes of the coned ring elements. However, the pressure ranges of the arrangements of the mentioned patents were effective only until about 1500 or some more hundred atmospheres. They could work at higher atmospheres but the efficiency would have made the devices uneconomical at such higher pressure ranges.
Since, however, for water jet cuttings and other purposes still higher pressures, for example, of 4000 atmospheres are often required, there remains a need to develop a new pumping means which would be economical in cost, maintenance, operation and which would be reliable in operation for a long an useful life.